Warp let-off mechanism for looms



0st. 1, 1963 w. P. ENLOE, JR 3,105,524

' WARP LET-OFF MECHANISM FOR LOOMS Filed April 24, 1961 3 Sheets-Sheet lINVENTOR. WINFRED PAGE ENLOE JR.

ATTORNEY Oct. 1, 1963 w. P. ENLOE, JR 3,105,524

WARP LET-OFF MECHANISM FOR LOOMS Filed April 24, 1961 s Sheets-Sheet 2'FLGE 2 a-ma I INVENTOR. WINFRED PAGE ENLOE JR.

ATTORNEY Oct. 1, 1963 w. P. ENLOE, JR

WARP LET-OFF MECHANISM FOR LOOMS 3 Sheets-Sheet 5 Filed April 24, 1961INVENTOR. WINFRED PAGE ENLOE JR.

w GE

ATTORNEY United States Patent 3,165,524 WARP LET-8F MEQHANISM FUR LGGMSWinfred Page Enloe, 3L, Lock Drawer 32, Roanoke, Ala. Filed Apr. 24,1961, Ser. No. 1115,166 11 Claims. (Cl. 13911tl) This invention relatesto warp let-oif mechanisms for looms and more particularly to a warptension responsive mechanism for actuating a positively driven warp feedmeans in which selector means are provided for rendering the tensionresponsive means effective only during certain portions of each weavingcycle when cyclical variations in warp tension are relatively small. Inthis way a high degree of precision is achieved.

In known warp feeding devices which respond to warp tension, it isdifiicult to achieve precise control primarily because of the variationsin magnitude of Warp tension which occur during each weaving cycle.Sudden and substantial increases occur, for example, when the layperforms its beat-up action against the fell of the cloth and alsoduring the establishment of the shed. More gradual variations attend thereduction in the effective radius of the warp beam as the warp threadsare let off.

if a warp feed control is not characterized by a high degree ofprecision, it is difficult to produce cloth of uniform quality andappearance where several looms are used because differences in controlof warp feed from loom to loom necessarily must result in cloth which isnot uniform and which in turn does not respond uniformly to the dyeingprocess.

If warp feed control is responsive to tension of the warp irrespectiveof wide variations which occur in warp tension during the weaving cycle,and particularly if warp tension is applied by spring means whose forceis variable, it is likely that unsightly set marks will be formed in thecloth due to undesired stretching of the warp threads while the loom isshut down.

A principal object of the invention is to improve the quality anduniformity of cloth by providing for greater precision in the control ofwarp feed mechanisms.

Another object of the invention is the provision of an improved tensionresponsive warp feed mechanism which is responsive only during certainportions of the weaving cycle when cyclical variations are relativelysmall.

Still another object of the invention is to provide an improved warpfeed mechanism for looms which is simple and reliable in construction.

The invention in one form as applied to a loom of the type characterizedby positive feed of the warp, comprises control means responsive to warptension for actuating the warp feed mechanism, and selector meansoperating in coordination with loom for rendering the control meanseifective only for portions of each weaving cycle during which cyclicalvariations in warp tension are relatively small. According to a facet ofthe invention the control means is rendered efiective to initiate acontrol operation only in response to movement of a thrust transmittingmember against the opposition of a thrust receiving means which affordsa substantially constant opposing force. Warp feed actuating movement ofthe thrust transmitting member occurs due to a slight increase in warptension.

For a better understanding of the invention reference may be had to thefollowing detailed description taken in conjunction with theaccompanying drawings in which FIG. 1 is a schematic view of a loom towhich the invention is applied; FIG. 2 is a view similar to FIG. 1 whichillustrates a modification of the invention depicted in FIG. 1 and whichrepresents one physical embodiment of a preferred form of the invention;FIG. 3 is a cross-sectional view of one of the elements depicted in FIG.2 and which is hereinafter sometimes referred to as a fluid motor;

FIG. 4 is an exploded perspective view showing the various parts of aselector valve constituting an essential feature of the invention; FIG.5 is a cross-sectional view of a conventional pressure regulating deviceforming an essential feature of the structure depicted in FIG. 2; FIG. 6is an enlarged view taken along the line designated 6-6 in FIG. 1; andin which FIG. 7 is an enlarged view taken along the line designated 77in FIG. 2 and which represents an alternative arrangement from thatdepicted in FIG. 6.

With reference to FIG. 1, the numeral 1 generally desig nates the warpbeam constituting main shaft 2 supported in fixed bearings 3 disposedone at each end of shaft 2. The warp threads are designated by thenumeral 4.

Since the warp feed means is of the positively driven type, a ring gear5 is securely aifixed to shaft :2 and is rotated by pinion 6 securelyaffixed to shaft 7. Also disposed about shaft 7 is a driving pinion 8 sothat rotation of driving pinion 8 imparts rotation to pinion 6 and inturn imparts clockwise rotation to ring gear 5 and to beam 1. Rotationof pinion 8 is effected by Worm gear 9 securely afiixed to stub shaft 10which in turn is mounted securely to ratchet wheel 11. Thus, rotation,of ratchet wheel 11 imparts rotary movement to stub shaft 10 and wormgear 9 and in turn results in advancement of beam 1 to let ofi warpthreads 4 as the weaving operation progresses.

For the purpose of imparting incremental rotary movement to ratchetwheel 11, an oscillatable element 12 is loosely pivoted about stub shaft10 so that element 12 may oscillate independently of ratchet wheel 11.Oscillatory motion is imparted to oscillatable member 12 by reciprocablyoperable driving rod 13. As is best shown in FIG. 6, a pawl 14 ispivoted by means of pivot pin 15 to oscillatable element 12. Also as isbest shown in FIG. 6, pawl '14 is biased by means of a tension spring 16for rotation in a counterclockwise direction about pivot pin 15 so as tohold the tooth portion 14A of the pawl 14- out of engagement withratchet teeth 11A of ratchet wheel 11. Thus with the parts occupying thepositions depicted in FIG. 6, oscillatable element 12 may move about thestub shaft 19 in opposite directions Without imparting rotary motion toratchet wheel 11. The right-hand end 14B of pawl 14 is biased into snugengagement with an expandable bulb 17 as will be more fully explainedhereinafter. Suflice it to say that bulb 17 is mounted on a cup shapedbracket 18 and is movable with the oscillatable element 12. Movement ofbulb 17 is accommodated by a flexible hose 19.

As will be apparent from FIG. 1, reciprocatory motion is imparted to rod13 by crank 22 which is pivoted about fixed pivot 21 and whichoscillates incrementally with the back-and-forth oscillation of the laysword 23 in known manner. Rod 13 is interconnected with crank arm 22 bymeans of rod 26. which is pivoted to crank 22 by the pin 24 and which isinterconnected with rod 13 by an adjustable connection 25, all of whichconstitutes well-known structure.

As is shown in FIG. 1, the warp threads 4 are fed over the whip rolls 26and 27 whose shafts are interconnected at their ends by a pair of links28. Links 28 and whip roll 26 are mounted on shaft 29 which is fixed inposition on fixed bracket 30 while whip roll 27 is rotatable about amovable shaft 31 which when moved about pivot 30 Patented Get. 1, 1963For the purpose of opposing clockwise rotation of links 28 and of whiproll 27 and associated parts about the pivot 29 and in accordance withthe invention, a thrust transmitting rod or element 38 is pivoted as bya pin 38A to one or both of the links 28. Interconnected with theright-hand end of thrust transmitting element 38 is a thrust receivingelement 39 which may be in the form of a fluid motor. Fluid motor 39comprises an outer tubular housing 40 as best shown in FIG. 3 togetherwith a diaphragm 41 to which the right-hand end of the thrusttransmitting element 38 is connected. It will be understood that fluidmotor 39 is of a conventional construction and that suitable liquidoccupies the space housing 40 to the right of diaphragm 41. It will alsobe understood that the diaphragm 41 in practice constitutes an innerrigid metallic cup-like element 43 to which is secured by suitable meansa flanged disc 44, the thrust transmitting element 38 being rigidlysecured to the structure comprising parts 43 and 44. Secured about thecupshaped element 43 is a grommet-shaped flexible diaphragm element 45having a rolled edge 46 which is securely captured (between the recessedrim of cup-shaped element 43 and the flange of disc 44 so as to form afluid tight junction therebetween. The other outer edge of thegrommet-like flexible material 45 is rolled as indicated at 47 and iscaptured between the shoulder portion 48 of the housing 40 and an innercylindrical element 49 secured to the right-hand end of the housing 40.Thus, the central part of the fluid motor constituting elements 43 and44 may move horizontally from left to right 'and vice versa due to theflexible nature of the grommet-like structure designated by the numeral45. With fluid occupying the space within housing 40 to the right ofdiaphragm 41, a motion to the right of thrust transmitting rod 38 due toa slight increase in tension of the warp threads 4 tends to drive theliquid designated by the numeral 50 through the selector means generallydesignated by the numeral 52 and causes the level of liquid 51 to risein pressure reservoir 53 and results in compression of the air therein.Preferably a suitable gauge 54 is provided whereby the pressure of thefluid 51 and of the air or other gas in the upper end of fluid reservoir53 may be determined. The fluid chamber 53 is quite large relative tothe fluid motor 39 and this fact is schematically depicted by means ofan auxiliary fluid reservoir designated by the numeral 55 which isinterconnected by a pipe 56 with the fluid chamber 53. Make-up gas maybe supplied through a schematically designated inlet 57 and check valve58 to the auxiliary reservoir 55.

From the description thus tar it will be understood that a substantiallyconstant pressure of the fluid system comprising reservoir 53 ismaintained and is arranged so as to oppose the movement of diaphragm 41upon an increase in tension of the Warp threads 4. It will also beunderstood that unless the force due to tension of Warp threads 4 isabove a predetermined value no motion to the right of the thrusttransmitting bar 38 will take place. If, however, tension on the warpthreads 4 is increased to .a value such that the force imparted tothrust transmitting element 38 is above' a predetermined value, fluidwill be driven through selector valve 52 when open and into pressurereservoir 53 so as to cause the level therein of the liquid 51 to risesomewhat.

Of course, an increase in tension of the warp threads 4 calls for alet-off operation of the beam 1. Such a letoif is etfected by controlmeans comprising the flexible bulb designated by the numeral 60 which isheld in place by a cup-shaped bracket 61 aflixed to suitable mountingstructure 62. Compression of flexible bulb 60 is eflected by a bracket63 secured by a pair of nuts 64 and 65 which are threadedly mounted onthe thrust transmitting element 38. The lower end of bracket 63designated by the numeral 66 is recessed so as to receive a part of theflexible bulb 60. Bulbs 60 and 17 and hose 19 are filled with liquid 67.Thus as the tension on warp 4 increases above a predetermined value,thrust transmitting element 38 moves bodily toward the right against theaction of diaphragm 41 and the pressure of fluid 51 and in so doingcauses the fluid 67 to impart pressure through flexible hose 19 to theflexible bulb 17 which in turn, as is best shown in FIG. 6, causes thepawl 14 to rotate in a clockwise direction about its pivot 15. Afterpredetermined clockwise rotation of pawl 14, its tooth 14A engages heratchet teeth 11A of ratchet 11. Thereafter, clockwise oscillation ofoscillatable element 12 about its stub shaft 10 imparts incrementalrotation to ratchet wheel 11. As is well understood, such rotationimparts incremental rotation to beam 1 and lets olf warp threads 4.During the time the warp threads are let off the pressure regulator 53exerts a substantially constant pressure on the fluid 51 and a quantityof fluid equal to the amount required to compensate for the length ofwarp let off is forced into chamber 53, thus keeping a substantiallyconstant warp tension. Upon reduction in the tension of the Warp threads4 whip roll 27 moves in a counterclockwise direction about the fixedpivot 29 and the operation may then be repeated.

As is well known, the warp tension is substantially increased at theinstant when the lay 37 engages the fell 34 'of the completed cloth.Furthermore it is well known that the formation on the shed 32 due tothe upenddown movement of the loom harness causes an increase in tensionof the warp threads 4. Thus with the jerky variation in the tension ofwarp threads 4 it is diflicult to obtain precision control of thelet-off mechanism since the tension responsive elements may responderratically at first to a fairly low tension during one part of theweaving cycle and later may be called upon to respond to a suddenlyincreased tension and hence precise control is naturally impossibleutilizing known devices.

In accordance with an essential feature of this invention, the portionot the weaving cycle during which tension varies substantially is ineifect eliminated and the tension responsive elements are allowed to seethe tension of the warp threads 4 only during a period of relativelysmall variations in tension which occur gradually primarily due to theprogression of the weaving cycle. To this end, selector valve 52 isprovided. As is best shown in FIG. 4 a housing element 68 is providedwith end caps 69 and 70 secured into a unitary assembly by four boltsone of which is shown at 71, the bolts extending through holes 71A in68, 69, and 70. The housing element 68 is provided with a cavity intowhich a machined sleeve 72 is fixedly secured. Sleeve 72 may be securedinto housing element 68 by known means such as by a pressed fit, setscrews not shown or the like. Sleeve 72 is provided with two openings 73and 74 which are diametrically opposite each other. The entire structureis mounted on bolts which extend through openings 76 and 77 respectivelyin depending ears 7S and 79 formed integrally with the end cap 70.

For the purpose of alfording communication with the space formed withinthe housing element 68 and sleeve 72 an inlet port 80 is formed withinthe housing element 68 and a similar port 81 is also formed within thehousing element 68. Port 81 is not shown in the perspective viewdesignated as FIG. 4, it being understood that port '81 is identical toport '80. As is best shown in FIG. 1, a pipe 80A is connected with theport 80 and a pipe 81A is interconnected with the port 81.

Disposed within the cavity formed within the housing element 68 andsleeve 72 is a rotor 82 securely afiixed to shaft 83. Shaft 83 extendsthrough opening 84 formed in end cap 69 and its other end is mounted onbearing 85 mounted in end cap 70. For the purpose of establishingintermittent communication between the ports 80 and 81 diametricalpassage 86 is formed within the rotor 82. The extremities 87 and 88 ofthe arcuate slots 73 and 74 in sleeve 72 preferably are approximatelysixty degrees apart and the rotor 82 is driven at a speed which isone-half the speed of the loom drive shaft so that for each revolutionof the loom drive shaft the rotor makes one-half revolution thusestablishing an effective spacing between extremities 87 and 88 of onehundred twenty degrees. Suitable conventional sealing means 89 areprovided about the periphery of the rotor 82 for forming an effectivefluid seal thereabout. Thus, communication is established between ports3! and 81 so long as passage 86 is in communication with the openings 73and 74- in sleeve 72. If, however, the openings 73 and 74 are covered bya solid portion of the rotor 82, communication between pipes A and 81Ais impossible.

According to the invention, as will be readily understood from the abovedescription, communication between pipes 80A and 81A is made only duringa portion of the weaving cycle during which the yarn tension of warpthreads 4 is substantially constant, such, for example, as during thetime when the shed 32 is open. In like fashion, communication is blockedby the solid portions of element 82 during erratic tension periods suchas during the beat-up of lay 37 or during other periods of high orextremely low tension. Thus, by the invention, precision control of thewarp feed mechanism is accomplished due to the fact that the rotatableelement 82 is driven in synchronism with the loom by chain which isdriven by the loom drive shaft 91 which in turn operates the lay sword23 and shaft 21 via links 92 and 92A. 7

As already explained, the arrangement depicted in FIG. 2 constitutes apreferred arrangement of an actual embodiment of the invention asdistinguished from the schematic arrangement depicted in FIG. 1. In FIG.2 the elements there shown are designated by the same numerals as areused to designate the corresponding elements in FIG. 1, except where theelements of FIG. 2 are of a different nature than the correspondingelements of FIG. 1. Such different elements forming the embodiment ofthe invention depicted in FIG. 2 are designated by different numeralsand are described in detail hereinafter.

With reference to FIG. 2, electromagnetic means are utilized to transmita control signal from a source of electrical energy 93 to the let-ofiactuating means rather than the hydraulic mechanism described in FIG. 1.In FIG. 2 such electromagnetic mechanism constitutes a conically shapedelement 94 which is threadedly mounted on the thrust transmittingelement 38 and which is locked in position thereon at a desired point bya lock nut 95. Disposed for engagement by the conically shaped element94 is a switch arm 96 forming a movable element of a suitablemicro-switch generally designated by the numeral 97. Micro-switch 97 isa normally closed device so that actuation of its switch arm 96separates its contacts and de-energizes the two conduits 98 and 99 andin turn effects de-energization of the solenoid 1th? securely afiixed toand movable with the oscillatable element 12 as best shown in FIG. 7. InFIG. 7 the pawl 14 is provided with a biasing spring 1411 which tends tourge the teeth 14A of pawl 14 into engagement with ratchet teeth 11Aformed about the periphery of ratchet wheel 11. Thus the devicepreferably is arranged so that the solenoid 1119 is normally energizedand normally maintains the pawl teeth 14A out of engagement with theratchet wheel teeth 11A against the action of biasing spring 101 asindicated in FIG. 7. When, however, the tension of the warp threads 4increases above a predetermined level, conically shaped element 94engages switch arm 96 and enects a de-energization of the solenoid andallows the spring 161 to rotate the pawl portion so that its teeth 14Aengage the ratchet teeth 11A. Thereafter, clockwise operation ofoscillatable element 12 about shaft 19 results in incremental rotationof the ratchet wheel 11 and the resulting let-otf of warp threads as iswell understood.

For the purpose of maintaining substantially constant pressure withinthe pressure reservoir 53 a known pressure regulating device generallydesignated in FIG. 2 by the numeral 192 is used. This device 102 isshown in cross-section in FIG. 5 and comprises an outer housingstructure 103 having an inlet port 1% to which a source of pressure airor gas is connected. Also the housing 103 is provided with an outletport 165 to which the fluid conduit 56 is connected. Mounted within thehousing 183 is a suitable diaphragm 106 which is biased downwardly by acompressional spring 197, the force of which may be adjusted by theexternally threaded sleeve 108 of the cap 109. Housing 1G3 is mounted onsuitable supporting structure by means of bolts 11% and the diaphragm106 is provided with a plunger element 111. Plunger 111 is provided witha reduced diameter portion designated by the numeral 112 at the lowerend of which a sealing cone 113 is arranged to control the cavity 114.Thus with the parts in the position depicted in FIG. 5, sealing cone 113is eifective to close the cavity 114. If, however, the pressure in theoutlet 1% is reduced, the pressure through passage 115 will be reducedand the enlarged throat portion 116 formed in partition wall 117accommodates transmission of this reduced pressure to the diaphragm 166.Thereafter the spring 1117 drives the plunger 111 downwardly so as toopen valve 113 and to re-establish communication between inlet 1G4 andoutlet 105. In this way the pressure within outlet and conduit 56 israised. Thus during let-0E, pressure is maintained substantiallyconstant in charnber 53 because a quantity of fluid is supplied in anamount to compensate for let-off movement of diaphragm 41. By the sametoken, if the pressure in the outlet port 195 or in conduit 56 becomesexcessive, pressure is transmitted through port and the opening 116 andbears against the lower surface of diaphragm 106 and drives the plunger111 upwardly against the biasing spring 107 to cause the sealing cone113 to prevent communication between inlet port 104 and the outlet port165. Excess pressure from outlet and is then bled ofi to atmospherethrough bleed passage 118 and port 119. In this way pressure in outlet1195 is maintained substantially constant as fluid is supplied graduallythrough the conduit 56 from tank 53 during movement to the right ofdiaphragm 4-1 and associated ports. Thus with the valve depicted in FIG.5 precise control of the pressure in fluid reservoir 53 is maintainedand in turn precise control of the tension of the warp 4 is achievedwhereby substantially constant warp tension is effected.

While I have shown and described a particular embodiment of theinvention I do not wish to be limited thereto and intend in the appendedclaims to cover all such changes and modifications as fall within thetrue spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A. warp let-oli mechanism for looms comprising Warp feed means, athrust transmitting element arranged to impart a force the magnitude ofwhich is dependent upon the tension of the warp, a thrust receivingelement arranged to obstruct movement of said thrust transmittingelement for forces below a predetermined magnitude and to accommodatemovement thereof for forces above a predetermined magnitude virtuallyirrespective of the position of said thrust receiving element, movementof said thrust transmitting element being effective to actuate said warpfeed means, and means operable in coordination with the loom forrendering said thrust receiving element ineiiective to accommodatemovement of said thrust transmitting element for a portion of eachWeaving cycle.

2. A warp let-off mechanism for looms comprising warp feed means, athrust transmitting element arranged to impart a force the magntude ofwhich is dependent upon the tension of the warp, a fluid motorinterconnected with said thrust transmitting element and with a sourceof fluid under pressure so that movement of said thrust transmittingelement is accommodated for forces exerted thereby in excess of apredetermined magnitude, and selector means operable in response tooperation of the loom for periodically connecting and disconnecting saidfluid motor from said source of fluid under pressure.

3. A warp let-off mechanism for looms comprising warp feed means, athrust transmitting element arranged to impart a force the magnitude ofwhich is dependent upon the tension of the warp, a fluid motorinterconnected with said thrust transmitting element and with a sourceof fluid under pressure so that movement of said thrust transmittingelement is accommodated for forces exerted thereby in excess of apredetermined magnitude, andselector means operable in response tooperation of the loom for periodically connecting and disconnecting saidfluid motor from said source of fluid under pressure, said selectormeans being eifective to connect said fluid motor and said source offluid under pressure when cyclical variations in warp tension are smalland to disconnect said fluid motor and said source of fluid underpressure when cyclical variations in warp tension are substantial.

4. A Warp let-01f mechanism for looms comprising warp feed means,movable thrust transmitting means arranged to impart a force themagnitude of which is dependent upon the tension of the warp, movablethrust receiving means interconnected with said thrust trans mittingmeans and arranged to prevent movement thereof for warp tension below apredetermined magnitude and to accommodate movement thereof for warptension above a predetermined magnitude, the force exerted by saidthrust receiving means in opposition to the force exerted thereon bysaid thrust transmitting means being virtually independent of theposition of said thrust receiving means and control means operable inresponse to predetermined movement of said thrust transmitting means foractuating said Warp feed means.

5. A warp let-off mechanism for looms comprising warp feed means,movable thrust transmitting means arranged to impart a force themagnitude of which is dependent upon the tension of the warp, movablethrust receiving means interconnected with said thrust transmittingmeans and arranged to prevent movement thereof for Warp tension below apredetermined magnitude and to accommodate movement thereof for warptension above a predetermined magnitude, the force exerted by saidthrust receiving means in opposition to the force exerted thereon bysaid thrust transmitting means being virtually independent of theposition of said thrust receiving means control means operable inresponse to predetermined movement of said thrust transmitting means foractuating said warp feed means, and selector means operable incoordinaation with the loom for rendering said thrust receiving meansineffective to accommodate movement of said thrust transmitting meansduring a portion of each weaving cycle irrespective of the momentarytension of the Warp.

6. A warp let-off mechanism for looms comprising a movable thrusttransmitting element arranged to move in one direction in response to anincrease in warp tension, a fixed thrust receiving fluid motorinterconnected with said thrust transmitting element and with a sourceof pressure fluid of substantially constant pressure so that movement ofsaid thrust transmitting element in said one direction is effected onlyfor warp tension in excess of a predetermined magnitude, and controlmeans responsive only' to movement of said thrust transmitting elementin said one direction for initiating a warp let-off operation. a 7. Awarp let-off mechanism for looms comprising a movable thrusttransmitting element arranged to move in one direction in response to anincrease in warp tension, a fixed thrust receiving fluid motorinterconnected with said thrust transmitting element and with a sourceof pressure fluid of substantially constant pressure so that movement ofsaid thrust transmitting element in said one direction is effected onlyfor warp tension in excess of a pre determined magnitude, control meansresponsive only to movement of said thrust transmitting element in saidone direction for initiating a warp let-off operation, and selectormeans interposed between siad fluid motor and its source of pressurefluid for periodically preventing movement of said thrust transmittingelement in said one direction.

8. A method of regulating warp tension in a loom comprising arranging amovable thrust transmitting element to exert a thrust in one directionin response to warp tension, interconnecting a thrust receiving elementwith said thrust transmitting element and arranging the thrust receivingelement to impart an intermittent force of substantially constantmagnitude and in opposition to movement of said thrust transmittingelement in said one direction said thrust receiving element beingarranged to impart the constant force during a part only of each loomcycle, and actuating feeding of the warp in response to predeterminedmovement of said thrust transmitting element in said one direction.

9. A method of regulating warp tension in a loom comprising arranging athrust transmitting element to exerta thrust in one direction inresponse to warp tension, interconnecting a thrust receiving elementwith said thrust transmitting element and arranging the thrust receivingelement to impart an intermittent force of substantially constantmagnitude and in opposition to movement of said thrust transmittingelement in said one direction virtually irrespective of the position ofsaid thrust transmitting element, the periods of intermittent forcecorresponding generally with each cyclical opening of the shed, andactuating feeding of the warp in response to predetermined movement ofsaid thrust transmitting element in said one direction.

10. A method of regulating warp tension in a loom comprising arranging athrust transmitting element to exert a thrust in one direction inresponse to warp tension, interconnecting a movable thrust receivingmeans of a thrust receiving element with said thrust transmittingelement and arranging the thrust receiving element to impart anintermittent force of substantially constant magnitude and in oppositionto movement of said thrust transmitting element in said one directionvirtually irrespective of the position of said thrust transmittingelement, the intervals between the periods of intermittent forcecorresponding generally to periods of substantial and sudden cyclicalchanges in warp tension.

11. A warp let-off mechanism for looms comprising a movable thrusttransmitting element arranged to move in one direction in response to anincrease in warp tension, a fixed thrust receiving fluid motorinterconnected with said thrust transmitting element and with a sourceof pressure fluid of substantially constant pressure so that movement ofsaid thrust transmitting element in said one direction is etfected onlyfor warp tension in excess of a predetermined magnitude, said fluidmotor constituting a housing and a flexible diaphragm disposed thereinin sealed relation to the inner surface thereof, said diaphragm beingconnected with said thrust transmitting element, and control meansresponsive only to movement of said thrust transmitting element in saidone direction for initiating a warp let-01f operation.

References Cited in the file of this patent UNITED STATES PATENTS2,375,316 Moessinger May 8, 1945 2,565,386 Marcy Aug. 21, 1951 2,661,773Kretzchmar Dec. 8, 1953 2,755,824 Hunt July 24, 1956 FOREIGN PATENTS525,839 Great Britain Sept. 5, 1940 337,155 Switzerland Apr. 30, 1959

1. A WRAP LET-OFF MECHANISM FOR LOOMS COMPRISING WARP FEED MEANS, ATHRUST TRANSMITTING ELEMENT ARRANGED TO IMPART A FORCE THE MAGNITUDE OFWHICH IS DEPENDENT UPON THE TENSION OF THE WARP, A THRUST RECEIVINGELEMENT ARRANGED TO OBSTRUCT MOVEMENT OF SAID THRUST TRANSMITTINGELEMENT FOR FORCES BELOW A PREDETERMINED MAGNITUDE AND TO ACCOMMODATEMOVEMENT THEREOF FOR FORCES ABOVE A PREDETERMINED MAGNITUDE VIRTUALLYIRRESPECTIVE OF THE POS-